The Gospel is, simply speaking, "Good News" that God announces to us! But what is that Good News?
It is the the news that the Son of God has come into this world in human flesh to reconcile us back to God (2 Corinthians 5:18). Jesus has come to give us peace with God!
Now, why would that be good news?
FIRST, THE BAD NEWS
In order to understand why this is good news, we need to first hear the bad news. It is like going to the doctor with a cancer that you didn't know that you had. Hearing from the doctor that you have cancer will no doubt be terrible news for you. But imagine if you heard that this doctor has found the treatment that will instantly cure your cancer. That would be good news indeed!
The cancer that is upon humanity is this: our alienation from God. The Bible calls this spiritual 'darkness’: We want to live our life without God, who is our Light (1 John 1:5). In fact, the Bible says we are at enmity with God, with minds that are constantly opposed to God's will (Romans 8:7). Listen to how the Bible describe our hearts before God: “the Lord saw that the wickedness of man was great in the earth, and that every intention of the thoughts of his heart was only evil continually” (Genesis 6:5). This is your heart and my heart.
Why is our heart like this? Because we want to be our own gods. We don’t want our Creator telling us what to do, how to run our lives. We want to be our own Boss. We want to be our own King. We want God out of the picture, even though everything in this universe was created for Him (Colossians 1:16), and He always wants nothing but our good (Deuteronomy 6:24). The Bible says that this act, the worshipping and serving of the creature — our selves! — over the Creator, is the root of all our problems.
And the result of our sin — our wilful alienation from God — the Bible says, is death (Romans 6:23). Since God is Life itself, to live an existence apart from God can only be death. What kind of death? Well, death in every way imaginable: death of our physical bodies, death of our relationships, death of our families, death of our society, and ultimately, the death of our souls eternally (Revelation 21:8).
THE GOOD NEWS OF JESUS
But listen to the good news: the Son of God, the God from God, the Light from Light, the “the radiance of the glory of God and the exact imprint of his nature” (Hebrews 1:3), came into this world as our Light to save us from our darkness. God the Son became human to reveal to us humans who God is: that although God is righteous and is right to punish us for our rebellion, that God is also loving. That God loves us more than we can ever imagine:
"For God so loved the world, that he gave his only Son, that whoever believes in him should not perish but have eternal life" (John 3:16)
God the Father crucified His own Son on the cross for our sins, so that, although we deserve to be cast into the “outer darkness” (Matthew 8:12) forever for choosing to live without God, Christ Himself experienced this darkness for us:
"Now from the sixth hour there was darkness over all the land until the ninth hour. And about the ninth hour Jesus cried out with a loud voice, saying, “Eli, Eli, lema sabachthani?” that is, “My God, my God, why have you forsaken me?"" (Matthew 27:45-46)
By being forsaken by God for our sins, and rising again from the dead on the third day, Christ has made a way for us to be welcomed back into the light of God’s presence.
In response to what Christ has done, we need to do two things:
Firstly, we need to repent. That means we need to turn away from worshipping created things of this world as our kings, as our gods, as our lords and saviours. Whether it’s self, money, sex, power, career, hobbies, family — etc. These are good things, but we must renounce these things as the ultimate controlling force in our lives.
Then secondly, we need to believe in Jesus. That is, we need to run to Jesus Christ! Go to Christ and throw yourself at Him as the only one who can save you from this darkness, this existence without God: “I am the bread of life; whoever comes to me shall not hunger, and whoever believes in me shall never thirst” (John 6:35): Jesus is the only one who can bring you into a real and a living relationship with God the Father that truly satisfies. To believe is also to look to Christ and what He has done for you (John 6:40) — Look! Christ forsook all his glory, and died a shameful death on the cross to show you this truth: God loves you! To believe in Jesus is to look and marvel at this love, that “while we were still sinners, Christ died for us” (Romans 5:8)
Behold God, holding out to you this free gift of relationship with Him for all eternity through His Son Jesus (Romans 6:23). All you need to do is to receive this free gift. You cannot earn this gift. Simply come to Christ, who is willing to bear the burden of all your darkness (Matthew 11:28).
So, if you ask, 'What is the Gospel?': The Gospel is God Himself:
Go on up to a high mountain,
O Zion, herald of good news;
lift up your voice with strength,
O Jerusalem, herald of good news;
lift it up, fear not;
say to the cities of Judah,
“Behold your God!” (Isaiah 40:9)
The Gospel is the Good News that through His Son's death and resurrection God has opened the way for relationship with Himself. Will you not respond to His invitation to you, “Come, for everything is now ready” (Luke 14:17)?